BrychanD/Shortest-Total-Path-Algo
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Fixed a potential issue with heuristics calculations

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This commit is contained in:
Brychan Dempsey 2021-10-21 22:16:53 +13:00
parent d40ebdabd2
commit 2a1c7c8c5e
1 changed files with 62 additions and 46 deletions
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108
ShortestTotalPath/Program.cs
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@ -8,56 +8,62 @@ namespace ShortestTotalPath
{ {
static void Main(string[] args) static void Main(string[] args)
{ {
Graph g = new(); // Take an approximate start time
for (int k = 0; k < 10; k++)
{
Graph g = new();
const int V = 10; const int V = 10;
List<Node> nodes = new(); List<Node> nodes = new();
// Use random numbers, but with a controlled seed (tests are repeatable) // Use random numbers, but with a controlled seed (tests are repeatable)
Random rand = new(2); Random rand = new();
// Create the nodes // double[] doubles = new double[] { 1.54, 1.37, 3.78, 8.54, 4.656, 7.334, 6.4643, 3.342, 3.456, 4.567 };
for (int i = 0; i < V; i++) // Create the nodes
{ for (int i = 0; i < V; i++)
Node newNode = new(i.ToString());
g.Nodes.Add(newNode);
nodes.Add(newNode);
}
// Create the links between nodes
for (int i = 0; i < V; i++)
{
for (int j = 0; j < V; j++)
{ {
if (i != j) Node newNode = new(i.ToString());
g.Nodes.Add(newNode);
nodes.Add(newNode);
}
// Create the links between nodes
for (int i = 0; i < V; i++)
{
for (int j = 0; j < V; j++)
{ {
if (nodes[j].Children.TryGetValue(nodes[i], out double value)) if (i != j)
{ {
nodes[i].Children.Add(nodes[j], value); if (nodes[j].Children.TryGetValue(nodes[i], out double value))
} {
else nodes[i].Children.Add(nodes[j], value);
{ }
nodes[i].Children.Add(nodes[j], 0.5 + rand.NextDouble() * 10); else
{
nodes[i].Children.Add(nodes[j], 0.5 + rand.NextDouble() * 10.0);
}
} }
} }
} }
} DateTime start = DateTime.Now;
// Take an approximate start time Algorithm a = new Algorithm();
DateTime start = DateTime.Now; Node n = a.Run(nodes[0], g);
Algorithm a = new Algorithm(); DateTime end = DateTime.Now;
Node n = a.Run(nodes[0], g); Console.WriteLine((end - start).TotalSeconds.ToString("N3") + " seconds");
DateTime end = DateTime.Now; Console.WriteLine(n.TotalTraversedLength);
Console.WriteLine((end - start).TotalSeconds.ToString("N3")); Console.Write("Path: ");
Console.Write("Path: "); for (int i = 0; i < n.TraversedNodes.Count; i++)
for (int i = 0; i < n.TraversedNodes.Count; i++)
{
Console.Write(n.TraversedNodes[i].Name);
if (i == n.TraversedNodes.Count - 1)
{ {
Console.WriteLine(); Console.Write(n.TraversedNodes[i].Name);
} if (i == n.TraversedNodes.Count - 1)
else {
{ Console.WriteLine();
Console.Write(" -> "); }
else
{
Console.Write(" -> ");
}
} }
} }
Console.ReadLine(); Console.ReadLine();
} }
@ -92,7 +98,7 @@ namespace ShortestTotalPath
{ {
// See if the node's traversed nodes contains all nodes in the graph // See if the node's traversed nodes contains all nodes in the graph
bool trueForAll = true; bool trueForAll = true;
foreach (var item in g.Nodes) foreach (Node item in g.Nodes)
{ {
if (!poppedNode.TraversedNodes.Contains(item)) if (!poppedNode.TraversedNodes.Contains(item))
{ {
@ -151,14 +157,24 @@ namespace ShortestTotalPath
// Another approach is to run simultaneous comparisons on chunks of data, i.e. break the queue into two-or-more // Another approach is to run simultaneous comparisons on chunks of data, i.e. break the queue into two-or-more
// sections and find the lowest of each section, then grab the overall lowest, but this requires additional // sections and find the lowest of each section, then grab the overall lowest, but this requires additional
// time to establish the required threads. For graphs > rank of 10, that may be a better approach // time to establish the required threads. For graphs > rank of 10, that may be a better approach
foreach (Node n in queue.Keys) if (queue.Keys.Count == 1)
{ {
// Compare Length plus heuristic to the current shortest length foreach (Node n in queue.Keys)
if (shortest is null || n.TotalTraversedLength + n.LocalHeuristic < length)
{ {
// new shortest found, replace the current shortest values
shortest = n; shortest = n;
length = n.TotalTraversedLength; }
}
else
{
foreach (Node n in queue.Keys)
{
// Compare Length plus heuristic to the current shortest length
if (n.TotalTraversedLength + n.LocalHeuristic < length)
{
// new shortest found, replace the current shortest values
shortest = n;
length = n.TotalTraversedLength + n.LocalHeuristic;
}
} }
} }
// Remove the node from the queue // Remove the node from the queue